1. Field of the Invention
The present invention relates to a liquid ejection head that ejects liquid such as ink, and a process for producing the same.
2. Description of the Related Art
A liquid ejection recording apparatus (ink jet recording apparatus) for ejecting a minute ink droplet from a minute ejection orifice is a mode of a recording apparatus for forming an image (in this case, a letter, a figure, a pattern, and the like are collectively referred to as an image, no matter whether they are meaningful or meaningless) on a recording medium such as recording paper. In general, a liquid ejection recording apparatus includes a liquid ejection head having an ejection orifice for ejecting an ink droplet, and an ink tank for holding ink to be supplied to the liquid ejection head. Ink is introduced from the ink tank to the liquid ejection head. An energy-generating element, for example, a heat generating element or a piezoelectric element, which is provided in a pressure chamber of the liquid ejection head, is driven based on a recording signal. Recording is performed by an ink droplet which is ejected from the ejection orifice onto a recording material. The liquid ejection recording apparatus is a so-called non-impact recording apparatus which has advantages including the ability of recording at high speed, the ability of recording on various kinds of recording media, and causing almost no noise in recording, and thus, is in widespread use.
In recent years, a still higher output speed of a printer is required, partly because in association with improvement in processing speed of a computer and a more minute ink droplet for the purpose of outputting a finer image, a higher ink droplet density is required. Demand for a higher speed of a large-scale printer or a networked printer is further prominent. A higher output speed of a printer can be attained by two factors: increase in the number of generated ink droplets per unit time, that is, increase in the ink ejection frequency; and increase in the number of the ink ejection orifices. Typically, a higher output speed of a printer is attained by both of the two factors. However, increase in the number of the ink ejection orifices means increase in the width of a nozzle array, which results in a longer liquid ejection head.
As described above, in order to provide a large number of ink ejection orifices, a production process is suitable in which a flow path forming member is formed of a photosensitive resin and the ejection orifices are formed by photolithography. However, when a flow path forming member is formed of a resin, as the liquid ejection head becomes longer, internal stress of the flow path forming member increases due to cure shrinkage and difference in linear expansion coefficient between a substrate and the photosensitive resin to form the flow path forming member. The internal stress may separate the substrate and the flow path forming member.
Accordingly, Japanese Patent Application Laid-Open No. 2003-80717 proposes a structure in which a groove which surrounds a liquid flow path is formed in the flow path forming member and side walls of the groove are formed in a serrated form with multiple minute serrations. Such a structure reduces stress on an ejection orifice plate to prevent separation of the flow path forming member even if the liquid ejection head is long.